The present invention relates to the fields of computer graphics and image manipulation. More particularly, the invention relates to techniques for generating three dimensional (3D) graphics directly from images, without constructing a 3D model explicitly.
Conventionally, a 3D modeling and rendering process is used for representing different views of a 3D scene. The usual steps in constructing a 3D model include: loading an image or previous saved work; displaying the image; identifying one or more object features in the image; finding the object features in 3D space; displaying a model of object features in 3D space; measuring lengths, distances and angles of the objects; and saving the work. These steps can be repeated until satisfactory results are obtained. This process requires a great deal of user interaction and is time-consuming. The user has to construct detailed models (e.g., polygon or wire frame) of the objects appearing in an image.
Once 3D models are obtained, the models may be animated by varying them and displaying the varied models at a predetermined frame rate. However, it is difficult to manipulate computer graphics representations of three-dimensional models, for example to rotate the object or "fly through" a scene. If many objects need to be displayed, or many surface textures need to be filled, the time required to compute new views can be prohibitive. The conventional 3D rendering process is thus compute intensive and also the rendering time depends on the complexity of the visible part of the scene.
On another note, one type of special effect in computer graphics is known as morphing. The morphing operation changes one picture to another by creating a smooth transitional link between the two pictures. The process preserves features associated with each image by mapping the features from a source image to corresponding features in a destination image. Morphing couples image warping with color interpolation. Image warping applies two dimensional geometric transformations on images to align their features geometrically, while color interpolation blends their colors. In this way, a seamless transition from one picture to another is achieved.
It can be expected that morphing between two views may be used to generate an effect of moving a camera while taking a movie. Distortions in the geometry of the images generated by morphing often arise when morphing is used to generate the effect of moving a camera. In a method known as view morphing, two parallel views taken by two cameras are interpolated and a special geometry is designed so that the distortions are eliminated. Any view from a point on the line connecting the two view points can be synthesized. However, the view morphing method cannot synthesize a view from any point in 3D space and can only synthesize views on a line connecting the two cameras.